In July 1965 an 11-km tunnel dug deep beneath the Alps was opened to traffic. Linking France and Italy, the Mont Blanc tunnel was a remarkable feat of engineering. Franco Cuaz, a consultant on the project and the tunnel's first operations manager, speaks to Mike Lanchin about the risks and challenges of the ambitious project.

Photo: Final preparations are made for the opening of the Mont Blanc Tunnel on the French-Italian border, July 1965. (Keystone/Getty Images)